Conduction Band Engineering of Half-Heusler Thermoelectrics Using Orbital Chemistry

Semiconducting half-Heusler (HH, XYZ) phases are promising thermoelectric materials owing to their versatile electronic properties. Because the valence band of half-Heusler phases benefits from the valence band extrema at several...

Влияние ионов неодима (III) на фотолюминесценцию сульфидов кадмия и цинка в полиакрилатной матрице

Nanoscale particles ZnS:Nd3+, CdS:Nd3+ and (Zn,Cd)S:Nd3+ were synthesized and doped in a polymerizing methyl methacrylate medium during the production of optically transparent polyacrylate composites of the composition PMMA/ZnS:Nd3+, PMMA/CdS:Nd3+ and PMMA/(Zn,Cd)S:Nd3+. The excitation of photoluminescence (FL) and FL of semiconductor structures in composites is associated with the transition of electrons from the valence band to the conduction band and to the levels of structural defects of semiconductor particles, followed by recombination at these levels. Based on changes in the excitation spectra of FL and FL composites, assumptions are made about the structure of particles, the distribution of Nd3+ ions in it and their effect on photoluminescence.

The Effect of Niobium and Rubidium Doping on the Energy Band Gap of a Lithium Tantalate (LiTaO3) Thin Film

Chemical solution deposition (CSD) is a technique for making a film by keeping synthetic arrangements on the outer layer of the substrate. The outcomes show that the band gap energy of the LiTaO3 film is 1 eV. Electrons are more effectively invigorated to the valence band than to the conduction band on the grounds that the energy required is not excessively huge. Niobium-doped LiTaO3 film has a band gap energy of 1.15 eV. A large amount of energy is needed for electrons to be energized from the valence band to the conduction band. The rubidium-doped LiTaO3 film has a band gap energy of 1.30 eV.

CALCULATION OF ELECTRONIC STRUCTURE OF 2D NaAu INTERMETALLIC LAYERS

Проведен расчет плотности состояний различной толщины 2D -слоев интерметаллида NaAu. 2D -слоев интерметаллида NaAu моделировались суперячейки NaAu (111) 2 х 2 х 2. Для монослойного 2D -слоя интерметаллида NaAu установлено наличие запрещенной зоны с шириной 1,87 эВ. Увеличение толщины толщины 2D -слоев интерметаллида NaAu до двух монослоев показал уменьшение ширины запрещенной зоны до 0,81эВ. Дальнейшее увеличение толщины 2D -слоев интерметаллида NaAu приводит к исчезновению запрещенной зоны, что указывает на переход полупроводник - металл для 2D -слоя интерметаллида NaAu толщиной три монослоя. Валентная зона 2D -слоя интерметаллида NaAu сформирована в основном Au 5d электронами, с незначительным вкладом Au 6s и Au 6p электронов. Зона проводимости NaAu образована в основном Au 6р электронами с незначительным вкладом электронов Na 3 s . The calculation of the density of states of various thicknesses of the 2D -layers of the intermetallic compound has been carried out. 2D -layers of intermetallic compound NaAu are simulated by supercells NaAu (111) 2 x 2 x 2. For a monolayer 2D -layer of an intermetallic compound NaAu the presence of a bandgap with a width of 1,87 eV has been established. An increase in the thickness of the 2D -layers of the intermetallic compound NaAu to two monolayers showed a decrease in the bandgap to 0,81 eV. A further increase in the thickness of the 2D -layers of the intermetallic compound NaAu leads to the disappearance of the band gap, which indicates a semiconductor-metal transition for the 2D -layer of the intermetallic compound NaAu with a thickness of three monolayers. The valence band of the 2D -layer of the intermetallic compound NaAu is formed mainly by Au 5d electrons, with an insignificant contribution from Au 6s and Au 6p electrons. The conduction band of NaAu is formed mainly by Au 6p electrons with an insignificant contribution of electrons Na 3s .

Velocity Map Imaging VUV Angle-Resolved Photoelectron Spectroscopy of Isolated Silver Sulfide Nanoparticles

The angle-resolved photoelectron spectroscopy of isolated silver sulfide nanoparticles was carried out by using velocity map imaging technique at the DESIRS beamline of SOLEIL synchrotron facility. The reported spectroscopy results were obtained after interaction of the synchrotron radiation with a polydisperse aerosol produced from aqueous dispersion of silver sulfide particles, approximately 16 nm in diameter. The photoelectron and UV-Vis-NIR absorption spectra were used to estimate the maximum energy of the valance- and the minimum energy of the conduction-band of the nanoparticles. With respect to the vacuum level, the obtained values were found to be 5.5±0.1 eV and 4.5±0.1 eV for the valence band maximum and conduction band minimum, respectively. The dependence of the asymmetry parameter on the electron energy along the silver sulfide valence band showed an onset of inelastic scattering at ~1 eV electron kinetic energy.

The bandgap energy of the dilute bismuth GaBi x Sb1−x alloy depending on temperature

The bandgap energy of the dilute bismuth GaBi x Sb1−x alloy vs. temperature is investigated in this study. Its reduced temperature-sensitiveness is because of the localized character of the valence band states (VBS). In order to describe the reduced temperature-sensitiveness of the bandgap energy, a new term including localized energy is added to Varshni's equation. It is found that the localized energy exhibits an increasing trend as the bismuth fraction increases, which indicates that the localized character of the VBS becomes strong with the increasing bismuth fraction. It is also found that the influence of the bismuth fraction on the temperature dependence of the bandgap energy of GaBi x Sb1−x is smaller than that of GaBi x As1−x . In addition, the element indium is undoubtedly a good candidate to lessen the bismuth fraction to realize that the spin-orbit-splitting (SOP) energy surpasses the bandgap energy in GaBi x Sb1−x .